Effect of N-doped carbon layer on the electrochemical performance of CoFe2O4 anode materials in lithium-ion batteries synthesized from spent LiCoO2 batteries

Cobalt ferrite (CoFe 2 O 4 ) nanoparticles are synthesized by sol-gel method using spent LiCoO 2 batteries as raw materials successfully. The CoFe 2 O 4 nanoparticles are subsequently coated with N-doped carbon by the carbonization of polydopamine obtained through self-polymerization of dopamine. The N-doped carbon layers with different thickness does not affect the structure and microstructure of CoFe 2 O 4 and they are coated on the surface of CoFe 2 O 4 nanoparticles confirmed by transmission electron microscopy. CoFe 2 O 4 /NC 30 exhibited superior electrochemical performance, such as high specific capacity (919.6 mAh/g for initial cycle at 0.1 A/g), excellent cycling performance (662.9 mAh/g after 200 cycles at 0.1 A/g) and rate capability (357.9 mAh/g at 2 A/g) for using as anodes in lithium-ion batteries compared with pristine CoFe 2 O 4 and other CoFe 2 O 4 /NC nanocomposites. The improved electrochemical performance could be ascribed to enhanced electrical conductivity and structural stability aroused by the N-doped carbon layers. • CoFe 2 O 4 /NC nanocomposites have been synthesized using spent LIBs as raw materials successfully. • The polydopamine derived N-doped carbon layer helps to improve electrochemical performance of CoFe 2 O 4 /NC nanocomposites. • The N-doped carbon layer does double duty: buffer layer and conductive agent. • This procedure provides a novel insight for broadening the recycling path of spent LIBs.